The present invention relates to a reference signal generator and method for measuring and controlling a rotating object.
In recent years, an ECU (Electronic Control Unit) has been used for the purposes of measuring the output performance and controlling the fuel injection rate, injection and ignition timing and the like of an automobile internal combustion engine (hereinafter referred to as an “engine”). Examples of patent applications relating to a method and apparatus for controlling the operation of an engine include Japanese Laid-open Patent Application No. 53-65531, Japanese Patent Publication No. 7-33809, Japanese Patent No. 3262003.
In an engine, the relationship between the output rotational speeds and strokes such as fuel injection, compression, combustion, and exhaust changes in accordance with the number of cylinders and the number of cycles. Therefore, these data are measured for each rotational angle of the crankshaft connected to the pistons in the engine when output characteristics such as the rotational torque of the engine, the rotational speed, and the rotational velocity are normally measured.
An ECU ordinarily controls an engine by controlling the fuel injection rate, injection and ignition timing, and other parameters with reference to the rotational angle of the crankshaft. The combustion characteristics and the output torque characteristics vary in accordance with this ignition timing control, and the amount of NOx, PM, and other toxic substances contained in the exhaust gas after combustion changes. Therefore, obtaining accurate measurement data and achieving optimal ignition timing are important techniques.
Conventionally, a cogwheel-shaped disk to which teeth (projections or notches) are provided at fixed intervals is mounted on the crankshaft of the engine as described in Patent Document 1, an electromagnetic pickup or an optical sensor detects the teeth when the crankshaft is rotating in order to detect the rotational angle, and the detection signal is used to carry out the above-described measurement and control.
With the internal combustion engine controller of Patent Document 1, the angular resolution is 1 degree, and there are therefore 360 teeth. The usual number of teeth is 60 or 36 (for resolutions of 6 degrees and 10 degrees).
However, the controller of such and internal combustion has the following technical problems.
Patent Document 1: Japanese Patent Publication No. 5-55709
Angular resolutions such as 1, 6, and 10 degrees noted above are insufficient for precise measurement and control. However, it is difficult to achieve greater resolutions due to physical limitations and production limits of the disk.
With ECU control in particular, the ignition timing must be predicted, and since the rotational state of the engine is not constant, the ignition timing is difficult to predict and real time control cannot be carried out.
With the problems of the aforedescribed prior art in view, it is an object of the present invention to provide a reference signal generator that can generate, in real time, reference signals for data measurement and engine control at a high resolution (e.g., 0.1 degree or less), in accordance with a rotational state that changes moment to moment, while using a conventional cogwheel-shaped angle detection mechanism.